Residents have reported seeing hundreds of dead fish in the Carnegie Lake. Why?
PRINCETON -- You may have seen dozens and dozens of dead fish floating in Lake Carnegie recently.
The New Jersey Department of Environmental Protection has determined that the dead fish floating in Lake Carnegie in Princeton is the result of a fish kill. Don't be alarmed -- it's not the prelude to a horror film or anything. But what's causing this large die-off?
The New Jersey Department of Environmental Protection (DEP) recently conducted an investigation and concluded that the die-off is the result of a "fish kill" -- when a local population of fish dies, and sometimes from environmental stress or other factors.
DEP spokesman Larry Hajna said that a conservation officer who conducted the investigation saw about 50 dead gizzard shad in the lake.
He said the issue could be due to changes in temperature or common bacteria like Aeromonas.
"Gizzard shad are sensitive to temperature changes, there is also common bacteria such as Aeromonas that can be a problem for fish already stressed due to spawning activity. So spring die-offs are not uncommon with this species," Hajna said.
He added, "an abundance of gizzard shad in one place at one time" could have made the fish "more susceptible to transmission of the bacteria."
The officer, Hajna noted, also "observed schools of hundreds of others all in good shape."
As to potential concerns about water toxicity, Hajna said the officer did not see "any other fish gulping at the surface, so water quality (is) probably not an issue."
He said, "Whenever we see primarily one species of fish (affected), we generally do not suspect a water quality issue."
The officers collected samples for testing at the DEP's fish pathology lab to confirm if the bacteria is responsible for the die-off, Hajna said.
The results are still pending.
"Again this is not an uncommon occurrence with this species which can tend to overpopulate an area, especially a smaller water body, and become more susceptible to disease transmission," Hajna said. "These outbreaks tend to run their course."
Spencer Kent may be reached at skent@njadvancemedia.com. Follow him on Twitter @SpencerMKent. Find the Find NJ.com on Facebook.